# stack light

> style of industrial warning lights

**Wikidata**: [Q7595956](https://www.wikidata.org/wiki/Q7595956)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Stack_light)  
**Source**: https://4ort.xyz/entity/stack-light

## Summary
A stack light is a style of industrial warning light designed to indicate the status or malfunction of a system. Also known as a signal tower or AndOn light, it functions as a visual indicator used in industrial environments to alert operators to specific conditions. It is classified as a specific subclass of the "tell-tale" warning device category.

## Key Facts
*   **Definition:** A stack light is a style of industrial warning light.
*   **Parent Class:** It is a subclass of "tell-tale," a class of light that indicates the malfunction of a system.
*   **Aliases:** Common synonyms include signal tower lights, indicator lights, AndOn lights, warning lights, industrial signal lights, tower lights, light towers, and the German term *Signalsäule*.
*   **Standardization:** The entity is classified under the United Nations Standard Products and Services Code (UNSPSC) **32151503**.
*   **Identifiers:** It holds the KBpedia ID "StackLight" and the Freebase ID "/m/0n48nf5".
*   **Digital Presence:** The entity has a sitelink count of 2 (Wikipedia and Wikimedia Commons) and is categorized under "Stack light" on Commons.

## FAQs
### Q: What is the primary function of a stack light?
A: A stack light serves as an industrial warning light used to visually indicate the status of machinery or processes. Specifically, it acts as a "tell-tale" device to signal when a system malfunction occurs.

### Q: What are other names for a stack light?
A: Stack lights are known by several names, including signal tower lights, light towers, indicator lights, and AndOn lights. In German-speaking regions, they may be referred to as *Signalsäule*.

### Q: How is a stack light classified in industrial taxonomies?
A: It is classified as a subclass of "tell-tale" indicators. Within product standards, it is identified by the UNSPSC code 32151503.

## Why It Matters
The stack light serves as a fundamental component in industrial automation and safety protocols. By providing a visual representation of a system's operational status, it allows for rapid human assessment of machine performance without the need for direct interface with a control panel. This visual signaling is critical in manufacturing environments where auditory warnings may be drowned out by machinery noise.

As a subclass of the "tell-tale" category, the stack light directly addresses the need for immediate malfunction notification. Its standardized presence under UNSPSC code 32151503 highlights its established role in the global supply chain for industrial equipment. The variety of its aliases—ranging from "signal tower" to "AndOn light"—demonstrates its cross-cultural adoption and essential utility in diverse manufacturing methodologies. Ultimately, the stack light matters because it bridges the gap between complex machine logic and human oversight, ensuring that errors or status changes are communicated instantly and clearly.

## Notable For
*   **Visual Indication:** Being a distinct style of industrial warning light that provides immediate visual feedback on system status.
*   **Broad Nomenclature:** Possessing a wide array of synonyms, including "AndOn lights" and "signal towers," reflecting its widespread use in various industries.
*   **Taxonomic Hierarchy:** Being a direct subclass of the "tell-tale" device class, linking it to core concepts of system diagnostics and malfunction indicators.
*   **Standardized Classification:** Holding a specific UNSPSC code (32151503), verifying its recognition in formal industrial product taxonomies.

## Body
### Definition and Classification
A stack light is defined structurally and functionally as a style of industrial warning lights. Within knowledge graphs and industrial taxonomies, it is identified as a **subclass of** "tell-tale." A tell-tale is defined broadly as a light that indicates the malfunction of a system. Therefore, the stack light operates as the physical apparatus fulfilling this warning function in industrial settings.

### Terminology and Synonyms
The device is recognized globally under various names, which are used interchangeably depending on the region or specific industrial application. Verified aliases include:
*   Signal tower lights
*   Indicator lights
*   AndOn lights
*   Warning lights
*   Industrial signal lights
*   Tower lights
*   Light towers
*   Signalsäule

### Identification and Standards
The entity is tracked across multiple databases and standards organizations.
*   **UNSPSC:** The Universal Standard Products and Services Code for a stack light is **32151503**.
*   **KBpedia:** The resource is mapped to the ID value `StackLight`, with references linking back to Wikidata item Q64139102 (accessed 2020-07-09).
*   **Microsoft Academic:** Prior to its discontinuation, the platform indexed the concept under ID **168459449**.
*   **Freebase:** The entity was indexed under the ID `/m/0n48nf5`.

### Digital and Media Presence
The "Stack light" entity maintains a digital footprint primarily through Wikimedia projects.
*   **Wikipedia:** The topic has a dedicated article titled "Stack light," available in the English language.
*   **Wikimedia Commons:** A dedicated category exists titled "Stack light," which contains related media, such as the reference image file `Stack_Light_Reference_Image.png`.
*   **Sitelinks:** The entity currently has **2** sitelinks connecting it to Wikipedia and Commons.

## References

1. KBpedia